PROJECT SUMMARY Chronic Obstructive Pulmonary Disease (COPD) is the 4th leading cause of death in the US with emphysema progression and lung function decline with evidence of poor mucociliary clearance and airway epithelial changes as well as alveolar destruction. We have found that in COPD there is a significant decrease in adherens junction protein E-cadherin, which is a primary component dictating cell-cell adhesion a finding which has been verified by several investigators and in large cohort studied. In this proposal, we will decipher the effects of E-cadherin regulation in promoting changes in epithelial function in the airways and parenchymal modeling and determine if increased E-cadherin protects the epithelia and the lungs from cigarette smoke (CS). We propose that decreased lung epithelial E-cadherin leads to loss of polarity of the epithelial cell, disrupts the epithelial barrier f and decreases ciliary beat frequency to promote airway dysfunction. Furthermore, we propose that loss of E- cadherin promotes parenchymal remodeling. We will dissect two specific mechanisms which could contribute to decreased protein levels. In Aim 1, we will determine if E-cadherin knockdown in cells, ex vivo trachea and mouse models lead to epithelial dysfunction and altered tissue integrity indicating that loss of E-cadherin with chronic smoke exposure or in patients with COPD serves a causal role in the development of COPD. Specifically, we will determine if lung E-cadherin loss alters epithelial polarity and decreases ciliary beat frequency, mucociliary clearance, and maintenance of the air surface liquid. In addition, we will determine if E- cadherin loss promotes parenchymal remodeling and inflammation using mouse models. In Aim 2, we will study novel mechanisms by which E-cadherin is decreased in the context of CS exposure and COPD. Specifically, we will study if epigenetic regulation of the promoter contributes to decrease in mRNA and protein abundance. Our data shows that CDH1 is methylated in an area rich with regulatory elements, so we will study these elements to determine what is altered with CS exposure. In addition, we have identified a post- translational modification which correlates with E-cadherin function in population studies. Specifically, we will determine if terminal fucosylation of E-cadherin increases its adhesion strength to enhance function. We have identified a specific identified polymorphism or a haplotype that is associated with functional changes and will genetically engineer this into a lung cell line to determine if these affect E-cadherin based cell-cell adhesion and function. In addition, we will determine if mice lacking this fucosylation have increased susceptibility to CS exposure. In Aim 3, we will perform proof of concept studies to determine if upregulation of E-cadherin serves as a therapeutic strategy in primary human cells and mouse models. In addition, we will determine if manipulating the pathways identified in Aim 2 upregulate E-cadherin and improve function in the context of CS exposure.